Epicyclic variable-speed gearing



Nov. 21, 1950 w. BRowN 2,530,646

EPICYCLIC VARIABLE SPEED GEARING Filed June 20, 1947 3 Sheets-Sheet 1 MMV No'v. 21, 1950 Filed June 20, 1947 w. BROWN 2,530,646

EPICYCLIC VARIABLE SPEED GEARING 3 Sheets-Sheet 2 gy/@mm- Nov. 2l, 1950 w. BROWN EPIcYcLIc VARIABLE SPEED GEARING 3 Sheets-Sheet 3 Filed June 20, 1947 C wwf/Wm Patented Nov. 21, Y 1950 UNITED STATES PATENT OFFICE Application June 20, 1947, Serial No. 756,077 In Great Britain October 7, 1938 Section 1l Public Law 690, August 8, 1946 Patent expires October 7, 1958 6 Claims. (Cl. 'i4-763) This invention relates to epicyclic variable speed gearing and is a development of the in vention described in the specification oi my copending United States Patent No. 2,168,600. It embodies a very similar arrangement of gearing and selector mechanism and in much the same way provides close-ratio gearing, but it also embodies one, two or more additional ratios without additional gearing and provides also new characteristics and advantages.

The invention in effect relates to gearing of the kind in which there are two adjacent epicyelic trains ofgearing A and B coupled for differential action and wherein, for one position at least of the selector mechanism the parts of the two trains are coupled together, so that, as in the earlier aforesaid invention, the planet carrier and annulus of the train A are connected respectively to the sun pinion and planet carrier of the other train B for rotation together, leaving the solitary sun pinion of the train A and the solitary annulus of the train B. y

One object of the invention has been to provide one or two additional ratios with a larger gear ratio and another object has been not only to retain the low gear ratio feature of the earlier aforesaid invention, but also to provide that the difference between the two low ratio changes (i. e. between the three low gear ratios) shall be such that the percentage decrease is greater than the percentage increase estimated from the middle gear ratio, which result is opposite to that provided by the earlier invention. The advantage of this opposite result is easily appreciated by the cyclist.

According to the invention the improved gear comprises two epicyclic gear trains and means for coupling the parts of the two said epicyclic gear trains together for differential action and to driving, driven and stationary members and is characterised in that the annulusv of the second train is permanently coupled to the driven member and means are provided (a) for coupling alterna tively the planet carrier or annulus of the first train to the driven member, (b) for coupling alternatively the sun of the second train or of `the first train to the axle for holding it stationary, :and (c) for coupling a driving member alterna tively to either the planet carrier or annulus of the rst train, so that for one increase and one decrease differential ratio from direct drive the gear ratio increase is less than the gear ratio decrease.

According to a second feature of the invention, means are provided for coupling the driving, driven and `stationary members to the 'parte of one of the epicyclic gear trains so as to obtain one or two normal or direct gear ratios therefrom. According to a third feature of the invention whilst the selector mechanism is positioned for use of one only of the epicyclic gear trains for a normal or direct gear ratio, the planet carrier of the other train is released.

According to a preferred embodiment incorporating the second feature of the invention, the selector mechanism is arranged so that for a 4- speed gear whilst the sun pinion of the train A is held stationary and the planet carrier of the train B is uncoupled from the driven member (the annulus of the train B being coupled to the driven member) the driving member may be coupled alternatively to the annulus of the train B for a normal or direct ratio, or to the planet carrier of the train B for a low ratio high gear, or whilst the driving member is connected to the annulus of the train B, the latter is uncoupled from the driven member (the planet carrier of the train B being then coupled to the drivenv member) for a low ratio low gear, or whilst the driving member is still coupled to the annulus of the train B and the planet carrier of the train B is still coupled to the driven member, the sun of the train A is released and the sun of the train B is held stationary for a fourth or low gear oi larger ratio: Or, for a fifth and high` gear ratio; the selector mechanism is arranged for the sun of the train A to be held stationary other for alternative holding of one or other of the suns to the axle shaft. By such arrangement, one lever will provide high, normal andlow ratios whilst the other lever will decide i whether the high and low ratios are small or large.

of the combinations above described, that is to say, giving the same gear ratios, but with diiferent couplings, without departing from the na ture of the invention.

In the accompanying drawing:

Fig. l is a sectional side elevation of a cyclen hub incorporating one example of speed gearl in accordance with the inventiom butin Other combinations of the coupling mechanisms may be provided as alternative to some which some of the sections are displaced angularly for the sake of clearance;

Fig. 2 is a cross section on line 2 2 of Fig. 1, showing the gear train A;

Fig. 3 is a cross section on line 3-3 of Fig. 1, showing the gear train B; y

Fig. 4 is a cross section on line 4 4 of Fig. 1, showing the dog clutch drive to the gear train B;

Fig. 5 is a cross section on line 5-5 of Fig. l, showing the paWl drive from the annulus of the gear train B to the hub body;

Fig. 6 is a perspective View of the pawl showing the side bevel or chamfer on one end, the purpose of which is described later;

Fig. 7 is a longitudinal sectionshowing a modified arrangement of the selector control within the axle;

Fig. 8 is a sectional side elevation of a modified construction of a cycle hub epicyclie variable speed gear incorporating the third feature of the invention.

As illustrated in Figs. l to 6, the improved gear is constructed as a four speed cycle hub giving three close ratios suitable for racing purposes, together with a fourth lowerk gear ratio, whilst Fig. 7 provides a fifth higher ratio. The gear, will, of course, have many other uses, but it is particularly designed and intended for such aforementioned use.

As shown in Fig. 1, the epicyclic gear train B consists of the annular gear ring or solitary an nulus II extended at one end to carry driving pawls I2 and having on its inner bore two sets of splines I3 and I4, in separate planes for alternative selection (see also Figs. 4 and 5). The splines I3 and I4 are parallel and concentric to the axis of the gear ring but the two sets of splines Jare displaced angularly from each other so that the splines I4 lie between the splines I3 when viewed from the end. Meshing with the` said annular gear ring I I are double planet pinions I5 carried on pins i6 which are extended through bearings in a planet cage I7 to form driving dogs I8, adjacent to and in a separate plane from the aforesaid sets of splines. This planet cage I7 carries driving pawls 26. The annular gear ring I9, of the gear train'YA is formed in the end piece 26 of the hub shell and meshing therewith are planet pinions 2| journalled on pins 2Ia mounted in a planet cage 22. This planet cage 22 has formed on it, or attached to it, a pinion 23, which meshes with the planet pinions I5 so completing the epicyclic gear train B (see Fig. 3).

Concentric with the foregoing parts lies an axle 24 on which is rotatably mounted a pinion 25 25 which meshes with the planet pinions 2| so forming the solitary sun pinion and completing the epicyclic gear train A (see Fig. 2). The sun pinion 25 carries on its face dogs 56. The axle 24 has splines 52 formed in it, upon which splines is keyed a sliding dog 5| which can engage with the dogs 5i! when required, so locking the pinion 25 to the axle, or freeing it at will.

Further, the planet cage 22 has formed in its bore a set of dogs 53 which can also be engaged by the sliding dog 5| so locking planet cage and pinion 22 to the axle or freeing it at will. A key 6| is provided passing through a slot in the axle 24 and located behind the sliding dog 5 land itselfadapted to be engaged by a shoulder 54e for l movement of the sliding dog, as described later. Additional to key 35, rod 36, and chain 31 (as 54h and 54o. The end shoulder 54a butts within the rod 36 when screwed home, and a collar 55 butts against shoulder 54b. Between the collar and key 35 is a spring 56, such spring being stronger in its partly compressed position than the spring'l 38 in its fully compressed position. The end of the rod 36 locates the key 35 relative to the shoulders 54h and 54e. A further spring 5'I acting against a collar 58 which rests against a shoulder on the axle 24 keeps the sliding dog 5| normally in engagement with the dogs 56 on the sun pinion 25 so locking it to the axle. The planet cage 22 is journalled into both ends of the planet cage I1 and also onto the pinion 25, so making the assembly a concentric one with itself and with the axle 24 and providing good bearing surfaces. The piece 26 also supports the planet cage I1 by being journalled over the seating diameter of the pawls 26.

Further, the gear ring II is centralised by the extensions I3V on the planet pinion pins I 6 engaging with its bore. The drive is taken from the left hand end of the gear by the driving pawls 2B to a supporting piece 26 which carriesratchet teeth 2 operating in a forward direction. This supporting piece 26 is mounted on ball bearings to a cone 2S screwed to the axle. The drive is taken from the other end of the gear by the pawls I2 to another supporting piece 29 which carries ratchet teeth 36 also operating in a forward direction (see also Fig. 5). Carried in a ball journal in this supporting piece 29 isv the driving member 3| which is further supported by a ball journal on a cone 32 screwed to the axle 24. An extension of the driving member 3| through the supporting piece 29 is journalled into the gear ring II so keeping it concentric with the axis of the whole assembly.

, Between and xed to the two end supporting described later) is a further rod 54 screwed into rodw36 and carrying three shoulders onstops 54a. i

" pieces 25 and 29 is mounted a shell 33 which performs the several functions of spacing the supporting pieces 26 and 29, forming a casing for the whole mechanism, and forming xing iianges 33a for buildingA a cycle wheel by means of spokes f in the usual manner. Y

iand the sleeve 34 isa cap 66. Rotatably mounted on the sleeve 34 and laterally positioned by a collar 39 formed on the sleeve and the said key 35, is a sliding dog 46 which engages with the driving member 3| for rotation with it, while still free to be moved laterally by the sleeve 34 and key 35. Also mounted on the driving member 3i in the application of the gearto a cycle hub, is a chain sprocket 4|, 4the mounting being by splines in the example described, so that i-.power can be transmitted to the driving member ...pinion 25 so locking it to the axle, and the dog 46 with the driving dogs I8 so coupling the driving member 3| to the planet carrier The dog .76.splnesjl3? 5514911 -movement 'being-possible since..

the spring, 56 is stronger than they spring 38,. l'.lurtherv pulling on the.- chain. 31. will next cause the dog 40 to engage with the: splines. Ill At this point the cap 6D against the sleeve 34 will come into contact with the sleeve 59 against the cone 32: and prevent any further. movement to the right of the, dog l0-. At this point the shoulder 54e on the rod 54 will also butt against the key 6I, so that by further pulling on the. chain 3i, the spring 5,6 will be compressed, pulling hey 6I to the right and with it the dog l.l The; dog 5I will, therefore. moveout of engagement with the dogs 50 on the pinion 25 and into engagement with` the dogs 53 on the combined planet carrier and sun pinion` 22, r 23, whilst still leaving the dog 40' engaged with. the splines I4 of the` solitary annulus` II, so giving gear ratios as described hereunder.

The complete epicyclic gear train is. such that if' a turning eiortbe applied to the driving dogs I8 on the planet carrier I'I the gear ring II will be carried round in the same direction at an increased speed, such speed being governed by the numbers of teeth in the gear ring II and sun pinion. 23, and also by the fact that this sun pinion 23 is rotated in the.l same direction by action of the gear ring I9 (which in this gear is attached to and rotates at the same speed as the gear ring II. by virtue of the pawls I2, supporting piece 29, shell 33, and supporting piece 26) acting on the planet cage 22 by means of the planet pin-ions 2 I` which mesh with gear ring I9 and sun pinion 25, which latter is fixed to the axle` 2.4, which is held in a non-rotatable manner in the cycle frame in this` instance. Since the supporting piece 2.6. rotates faster than the planet carrier I'In the ratchet teeth 2'I overrun the pawls Y and there` is no connection therefore between gear ring I9 and planet carrier I'I'. This arrangement of the selectors. gives a. low ratio over drive for high gear.

For direct drive7V dog 4D is moved to engage the splines I3 on gear ring II. Power is transmitted by the member 3I` through this dog to gear ring II by way of these splines.r Since it has been shown that gear ring. II. rotates faster than the pinion carrier IT at. all times this driving effort will be transmitted through the pawls I2, carried by gear ring I I to the supporting piece 29- and so to the hub shell.` Meanwhile the gears are idling and the other supporting piece 2E will over-run its co-acting pawls 20.

If, however, the. turning eiort be applied to gear ring II by the splines I4., and the pawls I2 disengaged from ratchet teeth 3B, as hereinafter described, the pinion carrier I1 will be carried round in the same direction at a reduced speed,. such speed being governed by the numbers. of teeth in the gear ring II and sun pinion 23,. and also by the fact that this sun pinion is rotated in the same direction by action of the gear ring I 9` (which in this gear is attached to and rotates at the same speed as the planet carrier I'I by virtue of the pawls 2u and ratchet teeth 21) acting on the planet cage 22 by means of the planet pinions 2l which mesh with gear ring i9 and sun pinion 25, which latter is xed to the axle 24 as previously described. This arrangement of the selectors gives a close ratio low gear.

If now in this latter gear position, the sun pinion 25 is disengaged from the axle and the planet carrier and sun pinion 22 be fixed to the axle, by movement of the dog 5I as above described, the planet carrier I'I and` with it the driven member will be carried round in thev same direction at a further reduced speed, such speed now being governed by the numbers of teeth in gear ring I Il, sun pinion 23, and planet pinions I5 only, the gear train A. now being inoperative. and

the sun pinion 25 revolving idly o-n the axle.

This arrangement of the selectors gives a second low gear of larger ratio from the normal or ii-xed ratio.

It will be seen that the ratio between the speeds of the gear ring' II and the planet carrier II is such that in all cases stated, the gear ring II rotates in the same direction as the planet carrier Il but at a greater speed than it, such varia.- tion in speed being dependent upon the geartrains inv operation.` Further, it will be seen that the ratio is such that` when the two annuli are coupled, i. e. when the pawls I2 are engaged, the dilrerential eiect of the two epicyclic trains greater than when the annulus I9 is coupled to` the planet carrier i'I by the pawls 20, this givingv the effect that the overdrive gear ratio is less than the underdrive. gear ratio. In the example described the planet pinions t5 are double pinions, but they can be single pinions if required, the double pinions being used to give a particular gear ratio. Alternatively the pinions 2| can be double pinions if this is necessary to give any other required ratio.

To demo-nstate the low ratio and larger bottom ratio which can be obtained by the improved construction, while using quite ordinary gear wheels, the following details are given.

The gear ring II and sun pinions 23 havek 56 and 20 teeth respectively while the double planet. pinions I5 have 14 and 20 teeth respectively. The gear ring I9, the planets 2l, and the Sun pinion 25 have 60, 15 and 30 teeth respectively. With such gears top gear provides 7.2% increase over direct drive, first low gear provides 7.65% decrease and second low gear provides 210% decrease. Using usual nomenclature gear ratios would therefore be` approximately 80, 921/2, 100 and 1071/4. The percentage decrease 7% or increase Ilr of the close or diierential ratios is less than half the percentage decrease 20 of the normal or direct ratio, which in turn is less` than the percentage increase of the normal or direct ratio which would be 25.

The action of disengaging the pawls I2 is as follows:

In moving from engagement from the first splines I3 the dog will first move laterally to a position behind the pawls I2 and will then rotate by virtue of the power communicated by the driving member 3l until it engages with the second set of splines I4 which are angularly displaced from the iirst splines. During this small arc of rotation no power is being transmitted from the driving member 3| to the gear assembly. and so the pawls I2 are not under load. These pawls `which have hitherto transmitted the drive to the shell, are formed with chamfered tail pieces 42 (see Fig. 6) which are adapted to be engaged by the sliding dog 4l) during thisv small arc of rotation so as to lift this end of the pawls to disengage the other end of the pawls by depressing them from the ratchet teeth of its c-oacting supporting piece 23. When such disengagement has been effected the dog 40 engages the second set of splines i4 and through them the drive is applied direct to the gear ring. The relationship of the pawl pivot pins of the pawl I2,

the driving splines it and the width of the dog 4e is such that when the dog takes up its driving` position against the splines I4 the pawls llorar.

7 held out of engagement with the teeth 3l) of the supporting piece 29.

It will be further noted that in changing from direct drive to low gear as above described in the event of the driver member 3| being stationary and the hub shell rotating, so over-running both sets of pawls I2 and 20, the drag of the mechanism will cause the sliding dog 40 to take up a position on the non-driving face of the first set of splines I3. To enable the sliding dog 4U to move laterally the chamfer 42 is cut on the pawls of the first set (see Fig. 6) so that the sliding dog will be able by virtue of the wedging action of this chamfer to move axially while elevating the pawls I2 and then drop back to the non-driving face of the second set of splines I4. In taking up the drive again, the sliding dog 4I] will elevate the pawls I2 by their rearmost shape before driving on the splines I4 as previously described. The pawls I2 and 20 provide a free wheel action in all the gear ratios.

As shown in Fig. '7 the selector mechanism at the right hand end is the same as shown in my co-pending United States Patent No. 2,168,600, the key 35 being positively secured to the rod 36. In place of the extension rod 54 a further rod 62 is provided, xed to the key 6 I the rod being provided with a spring 63 which abuts against a collar 64 screwed into the axle. The rod is provided with the usual operating chain. The spring 63 is arranged to be stronger than the spring 5l and thus normally would hold the dog i in engagement with the dogs 53 on the planet carrier 22, to lock it to the axle 24. By pulling the rod 62 outwards (to the left) the dog 5I releases the part 22 and engages the dogs 56 to lock the pinion 25 to the axle.

With the above construction it will be seen that the selector rod 36 can be operated to provide high, normal (direct) or low, whilst the selector rod 62 decides whether the high or low shall be low ratio or larger ratio according to whether the pinion 25 or the planet carrier and pinion 22, 23 is held stationary, respectively.

Obviously the invention is not limited to the details of the example above described, many of which could be modified without departing from the nature of the invention, the principal features of which are as follows:

1. The sun pinion of the gear train B is geared to alternative members of the gear train B by means of the epicyclic gear train A in such manner that the said sun pinion is driven in the direction of the driving and driven members, so reducing the overdrive or underdrive ratio existing between the driving and driven members of the epicyclic gearY train B.

2. The sun pinion of the gear train Bl is geared to that member of the train B which will reduce the overdrive ratio of the gear train to a greater extent than it reduces the underdrive ratio of the gear train.

3. The sun pinion of the gear train B can be locked separately from the sun pinion of the gear train A so allowing the gear train B to be used alone in the orthodox manner to give an underdrive ratio, and not in conjunction with the secondary gear train, so giving four gear ratios.

4. The driving member can transmit power to the driven member in a ratio of one to one, or give an overdrive ratio and two underdrive ratios, such ratios being adjustable by the numbers of teeth in the gear trains, the rst overdrive and underdrive being of lower ratio to the direct one toone 'gear ratio than that obtainable in an sun pinions a further gear ratio increase can bel obtained being equal to the increase obtained by using the primary train only as in the case of an underdrive ratio as set out in feature 3. This separate control by spring and rod gives a total of ve speeds comprising two increases, two decreases, and one direct drive.

6. All rotating parts are so journalled to each other and to the casing of the gear as to be concentric one with another and with the axis of the casing under all conditions and with a minimum of relative movement.

7. The gear ratio can be changed at will by means of movable couplings between the driving and driven members while the gear is in use.

8. All gear trains are journalled on either side of said gear trains to eliminate strains due to overhung loads.

9. The relative speeds of the low ratio gear trains are kept lower than in orthodox epicyclic gears thus increasing life of gears and also the load transmissible for a given size of gear.

One advantage of the construction of the rst example of gear above described is that the planet gears of the train A, whilst the fourth and fth or larger ratio gears were in use, were compelled to rotate at relatively high speeds, and the present invention has for its object an improved construction and arrangement of parts to overcome the said disadvantage.

In a preferred embodiment of the invention incorporating the third feature of the invention and compared with the examples above described, means are provided for uncoupling the planet carrier of the gear train A from the sun pinion of the gear train B when such sun pinion is held stationary.

In such preferred embodiment of the invention, the improved change speed gear is characterised in that the annulus of the gear train A is coupled to the driven members and means are provided (a) for coupling alternatively the planet carrier or annulus of the gear train B to the driven member (b) alternatively for coupling the sun of the train B to the axle for holding it stationary or for causing the sun of the gear train B to rotate with the planet carrier of the gear train A about the stationary sun pinion of the gear train A and (c) for coupling a driving member alternatively to either the planet carrier or annulus of the gear train B.

According to a constructional embodiment of the invention, incorporating this third feature the selector mechanism is arranged so that for a 4-speed gear whilst the sun pinion of the gear train B is constrained to rotate with the planet `carrier of the gear train A about the stationary sun pinion of the gear train A and whilst the planet carrier of the gear train B is uncoupled from the driven member (the annulus of the gear train B being coupled to the driven member) the driving member may be coupled alternatively to the annulus of the gear train B for a normal or direct ratio, or to the planet carrier of the gear train B for a low ratio high gear, or whilst the driving member is connected to the annulus of the gear train B, the latter is uncoupled from the driven member (the planet carrier of the gear train B being then coupled to the driven member) `for a lowratio lowgear,- or whilst Vthe driving member is still coupled to the annulus of the train B and the planet-carrier of the train B is still coupled to the driven member, the sun of the train B is held stationary whilst the gear trainA is permitted to run idle for a fourth or W gear of larger ratio; or, for a fifth and high gear of wider ratio, the selector mechanism is arranged asV for the fourth gear ratio but with the driving member connected to the'planet carrier of the gear train B and the annulus of the gear train Bis connected to the driven member.

In such preferred embodiment of the invention the solitary sun pinion of the gear train A is permanently held stationary and4 the means for coupling and uncoupling the planet carrier of the gear train A from the sun pinion of the gear train B also embodies means for holding the sun pinion of the gear trainB stationary;

As shown inFig.` 8 the gear has many parts of the same construction as described and illustrated in Fig. l and such parts are for simplicity given the same reference numbers.

The following are the principal differences:

1. The sun pinion is permanently secured by 4splines 24a anda nut 24h to the axle 24, and such sun pinion does not have the dog teeth of the first example.

Z, `The planet carrier or cage 2,2 is severed from the sun pinion 23 and the disc-like back part of such cage is formed with a ring of internally cut teeth 22e. The pinion 23 is provided with long dogs 53d equivalent tothe dogs 53 vof the nrst example, whilst `such dogs 5,3aextend to Within a short distance of the said ring of internally cut the axle 24 and formed on its outer periphery` with dogs 61 adapted permanently to engage with the long dogs 53a and to be engaged with or disengaged irom the ring of internally cut teeth 22e, in the cage 22. Between. the collar 66 and the key 65 is a ring tanotched on its face to engage the ends `of the key, the other `face of such ring forming a thrust bearing for the collar B8. This rotatable collar 66 also has internally formed dog teeth B8 adapted to engage dogs 69 formed on or permanently secured to the axle 24 immediately against the `pinion 2.3. The sliding key w65 is adapted to be operated by the rod .46 in the same manner as was. the sliding dog .54. The lsliding parts are kept normally so that the cage 22 is united to the pinion 23 for rotation together by means of the spring 53h above described.

Thus it will be seen that, for the direct and low ratio gear changes the sliding key 65 remains in a position in which the cage 22 is connected to the pinion 23, the selector mechanism operating exactly as described in the iirst example.

For the fourth or extra lov/ gear position, the rod t6 moves the sliding key 65 so that the dogs El of the collar 6B disengage from the internally toothed ring 22o in the cage 22 Whilst the internally formed dog teeth 68 on the collar engage the dogs 69 on the axle, so that the cage 22 is thus released Whilst the pinion 23 is held stationary as the long dogs 53a are still engaged with the external dogs B1 on the collar 6E.

For providing a fth gear ratio, separate control mechanism would preferably be employed for moving the sliding key 65 and its collar 65 in the sameway as described for moving the sliding dog 5l (see Fig. 7) so that whilst the collar B6 was in a position to hold the pinion 23 stationary the other selector 4D could be moved to the position shown in Fig. 3 previously required for the high low ratio gear.

The 'construction of the present invention shown in Fig. 8 embodies several minor features oi construction such as locating the pawls (not shown) ot the free W-heel mechanism in a groove 2cd and extending the cage 22 of the gear train A with an annular flange 22d to locate 'it against one side of groove for the adjacent pawls.. Also, instead of double planet pinions l5, single planet pinions 5a are employed which provide room for the spring 53h which returns the sliding collar 65 but this alteration does not alter the fact that the underdrive gear ratio is greater than the overdrive gear ratio. Thus in one arrangement the following ratios were obtained, approximately:

1st-25% underdrive. 2nd-10% underdrive. 3rd-Direct drive. 4th-9.1% overdrive. 5th-33 ,1/3 overdrive.

The invention is obviously not limited to all the details of construction above described, some of which may be modied without departing from the nature of the invention.

What I claim is:

l, An epicyclic variable speed gear comprising iirst and second epicyclic gear trains, each consisting of a sun, a planet carrier and an annulus nfl-amber,` driving member, driving selector means for selectively coupling said driving member alternatively to the planet carrier or annulus oi the gear ytrain for overdrive rat-io and either direct drive or underdrive ratio respectively relative to said driving member, a xed member, a driven member, pavvl and ratchet means connecting the planet carrier of the first gear train to thedriven member, second pavvl and ratchet means connecting the annulus of the first gear train to the driven member, means for tripping the pawl of said second pawl and ratchet means out'of engagement with said driven member when thev driving selector is coupled to the annulus of the'rst gear train whereby drive is transmitted tosaid drivenmember alternatively through said first .or saidsecond pawl and ratchet means from the planet carrier of the rst gear train or the annulus of the rst gear train, means connecting the sun member oi the rst gear train to the planet carrier of the second gear train and means for connecting the sun member of the second gear train to said xed member, characterised in that the annulus of the second gear train ispermanently connected to the driven member, whereby the two gear trains may be coupled for overdrive and underdrive ratios, so that relative to the direct ratio, the gear ratio increase is less than the gear ratio decrease.

2. An epicyclic variable speed gear according to claim 1 characterised by means for disconnecting the planet carrier of the second gear train from the sun member of the rst gear train so that the second gear train may run idle and for coupling the sun member of the rst gear train to the xed member, so that first gear train may provide additional overdrive and underdrive rail tios from the alternative positions of the driving selector means aforesaid.

3. An epicyclic variable speed gear according to claim 1 characterised by means for disconnecting the planet carrier of the second gear train from the sun member of the first gear train so that the second gear train may run idle and for coupling the sun member of the rst gear train to the fixed member, so that the rst gear train may provide additional overdrive and underdrive ratios from the alternative positions of the driving selector means aforesaid, and further characterised by actuating means for moving the said driving selector between its alternate positions and tripping said pawl and lost motion mechanism coupling said actuating means to the means for uncoupling the planet carrier of the second gear train from the sun member of the first gear train and for coupling the sun member of the first gear train to the fixed member, said driving selector being arrested after reaching its pawl tripping position, further movement of the actuating means causing the uncoupling action aforesaid.

4. An epicyclic variable speed speed gear according to claim 1 characterised by means for disconnectingthe planet carrier of the second gear train from the sun member of the iirst gear train so that the second gear train may run idle and for coupling the sun member of the first gear train to the fixed member, so that the first gear train may provide additional overdrive and underdrive ratios from the alternative positions of the driving selector means aforesaid, further characterised by actuating means for moving the driving selector between its alternative positions and separate actuating means for disconnecting the planet carrier of the second gear train from the sun member of the rst gear train so that the second gear train may run idle and for coupling the sun member of the first gear train to the fixed member, so that the first gear train may provide additional overdrive and underdrive ratios from the alternative positions of the driving selector means aforesaid.

5. An epicyclic variable speed gear comprising rst and second epicyclic gear trains, each consisting of a sun, a planet carrier and an annulus member, a driving member, driving selector means for selectively coupling said driving member alternatively to the planet carrier or annulus of the first gear train for overdrive ratio and either direct drive or underdrive ratio respectively relative to said driving member, a fixed member, a driven member, pawl and ratchet means connecting the planet carrier of the first gear train to the driven member, second pawl and ratchet means connecting the annulus of the lirst gear train to the driven member, means for tripping the pawl of said second pawl and ratchet means'out of engagement with said driven member when the driving selector is coupled to the annulus of the first gear train whereby drive is transmitted to said driven member alternatively through said rst or said second pawl and ratchet means from the planet carrier of the first gear train or the annulus of the rst gear train, means connecting the sun member of the rst gear train to the planet carrier of the second gear train and means for connecting the sun member of the second gear train to said fixed member, one

fof said connecting means being disconnectable,

characterised in that the annulus of the second gear train is permanently connected to the driven member, whereby the two gear trains may be coupled for overdrive and underdrive ratios, in such manner that relative to the direct ratio, the overdrive ratio is less than the `underdrive ratio, further characterised by means for uncoupling the sun member of the second gear train from the fixed member so that the second gear train may run idle and for coupling the sun member of the first gear train to the fixed member so that the iirst gear train may provide additional overdrive and underdrive ratios from the selective coupling aforesaid of the driving member.

' 6. An epicyclic variable speed gear according to claim 5 further characterised by actuating means for moving the said driving selector and said pawl tripping means and lost motion means connecting said actuating means to the means for uncoupling and coupling the sun members to and from the fixed member so that while the said driving selector and pawl tripping means are p0- sitioned for giving a decrease ratio, said actuating means may be used to e'ect said uncoupling and coupling of the sun members.

WILLIAM BROWN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Y Number Name Date 1,045,238 Winkler Nov. 26, 1912 2,168,600 Brown Aug. 8, 1939 2,301,852 Brown Nov. 10, 1942 FOREIGN PATENTS Number Country Date 5,988 Great Britain pDec. 11, 1913 13,728 Great Britain June 12, 1912 221,146 Switzerland Aug. 1, 1942 

